It is proposed to identify and characterize lymphocytes separated from tumors both in man (carcinoma of the lung, esophagus, and other nonlymphoid primary and metastatic thoracic tumors) and in an animal model (Sarcoma I and BP8 tumors in inbred mice). Lymphocytes harvested from other lymphoid sites within the tumor bearing animal (draining lymph nodes and peripheral blood with human tumors and, in addition, spleen and thymus in mice) will be compared to the "tumor separated" lymphocyte. Cell-mediated immunity and humoral factors that may affect it (blocking antibody) will be studied by mixed lymphocyte culture stimulation, production of recruiting factors (chemotactic factor, macrophage inhibiting factor, blastogenic factor) and by direct cellular cytotoxicity.